Snowmobiles have traditionally used two-stroke type engines for power generation. Two-stroke type engines generally provide relatively high power-to-weight and power-to-size ratios, which are extremely desirable characteristics in an engine for a snowmobile. Other highly desirable characteristics of two-stroke engines in regards to snowmobiles include the relative simplicity of these types of engines and the relative ease of integration with systems, aided by the relatively high power-to-weight and power-to-size ratios of these engines.
However, recently there has been a trend to decrease exhaust emissions from internal combustion engines, especially two-stroke engines, due to environmental concerns and an increase in regulations related thereto. Generally, two-stroke engines inherently have higher exhaust emissions than their four-stroke counterparts due to: 1) the necessity of opening the exhaust ports subsequent to complete ignition of the fuel/air mixture, 2) unburned fuel escaping the exhaust port during the intake charging of the cylinder, and 3) lubrication oil mixing with the intake charge.
Lower emissions-producing four-stroke engines have generally not been used with snowmobiles due to the relatively lower power-to-weight/size ratios of these types of engines. Snowmobile performance is extremely sensitive to increases in weight and the relative compact chassis and body of a snowmobile limits the space available for the engine. Additionally, four-stroke engines can be relatively more difficult to integrate into vehicles, such as a snowmobile, due to the engine's relative complexity.
It is known outside the art of snowmobiles to use a turbocharger in conjunction with a four-stroke engine to increase the power output and fuel efficiency of the engine. However, a turbocharged V-twin engine has not previously been considered feasible for utilization with a snowmobile.